1. Field of the Invention
This invention relates generally to nonvolatile random access magnetic memory devices.
More particularly, the present invention relates to an improved Hall effect ferromagnetic random access memory cell and its method of fabrication.
2. State of the Art
The Hall effect is an electromagnetic phenomenon whereby a conductor carrying an electric current perpendicular to an applied magnetic field develops a voltage gradient which is transverse to both the current and the magnetic field. This principle has been applied in many electromagnetic devices, including those constructed with semiconducting materials to produce field effect transistors (FETs).
FETs are well known and have been used to create digital memory devices. For example, U.S. Pat. No. 5,295,097 to Lienau teaches a Hall effect memory device comprising a domain made of ferromagnetic material, substantially surrounded by a conducting coil. When the coil is supplied with an electric current, a residual magnetic field is created in the domain, the polarity of this magnetic field depending on the direction of the current of the coil. This is how digital information is written to the domain. A FET is disposed so as to be perpendicularly penetrated by this field, the differential voltage across the drains of the FET indicating the polarity of the magnetic field. This is how digital information is read from the domain.
While these devices are known in the art, they are somewhat difficult and costly to construct. Additionally, fabrication constraints affect the density of placement of the devices on a computer chip, and thus affect the overall size of digital computer components. It would be desirable to have a hall effect ferromagnetic random access memory device that is less expensive and less difficult to fabricate, and which is also smaller and may be disposed on a microchip in greater density.